JDBC and JCA connection pools—Connection pool Metrics include the average size of a connection pool, the number of connections, the average number of threads waiting for a connection, the average wait time in milliseconds for a connection, and the average time for the connection.

try to check in the PMI browser in your WebSphere admin interface if the metric is there, if it's not available as a actual messurepoint in the websphere admin console it will not end up in CA APM either. An other point could be that some of the metrics are not reported when they dont have a count, again something to verify with the metric browser in the admin console.